ALSA: hdspm - prevent reading unitialized stack memory

Original patch by Dan Rosenberg <drosenberg@vsecurity.com> under commit
e68d3b316ab7b02a074edc4f770e6a746390cb7d. I'm copying his text here:

The SNDRV_HDSPM_IOCTL_GET_CONFIG_INFO ioctl in hdspm.c allow unprivileged
users to read uninitialized kernel stack memory, because several fields
of the hdspm_config struct declared on the stack are not altered
or zeroed before being copied back to the user.  This patch takes care
of it.

Signed-off-by: Adrian Knoth <adi@drcomp.erfurt.thur.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/rme9652/hdspm.c

@@ -6081,6 +6081,7 @@ static int snd_hdspm_hwdep_ioctl(struct snd_hwdep *hw, struct file *file,
 
 	case SNDRV_HDSPM_IOCTL_GET_CONFIG:
 
+		memset(&info, 0, sizeof(info));
 		spin_lock_irq(&hdspm->lock);
 		info.pref_sync_ref = hdspm_pref_sync_ref(hdspm);
 		info.wordclock_sync_check = hdspm_wc_sync_check(hdspm);